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Discovery of an Intermediate-luminosity Red Transient in M51 and Its Likely Dust-obscured, Infrared-variable Progenitor

Jencson, Jacob E. and Adams, Scott M. and Bond, Howard E. and Van Dyk, Schuyler D. and Kasliwal, Mansi M. and Bally, John and Blagorodnova, Nadja and De, Kishalay and Fremling, Christoffer and Yao, Yuhan and Fruchter, A. and Rubin, David and Barbarino, Cristina and Sollerman, J. and Miller, Adam A. and Hicks, Erin K. S. and Malkan, Matthew and Andreoni, Igor and Bellm, Eric C. and Buchheim, Robert and Dekany, Richard and Feeney, Michael and Frederick, Sara and Gal-Yam, A. and Gehrz, R. D. and Giomi, Matteo and Graham, Matthew J. and Green, Wayne and Hale, David and Hankins, Matthew J. and Hanson, Mark and Helou, George and Ho, Anna Y. Q. and Hung, T. and Jurić, Mario and Kendurkar, Malhar R. and Kulkarni, S. R. and Lau, Ryan M. and Masci, Frank J. and Neill, James D. and Quin, Kevin and Riddle, Reed and Rusholme, B. and Sims, Forrest and Smith, Nathan and Smith, Roger M. and Soumagnac, Maayane T. and Tachibana, Yutaro and Tinyanont, Samaporn and Walters, Richard and Watson, Stanley and Williams, Robert E. (2019) Discovery of an Intermediate-luminosity Red Transient in M51 and Its Likely Dust-obscured, Infrared-variable Progenitor. Astrophysical Journal Letters, 880 (2). Art. No. L20. ISSN 2041-8213. doi:10.3847/2041-8213/ab2c05.

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We present the discovery of an optical transient (OT) in Messier 51, designated M51 OT2019-1 (also ZTF 19aadyppr, AT 2019abn, ATLAS19bzl), by the Zwicky Transient Facility (ZTF). The OT rose over 15 days to an observed luminosity of M_r = −13 (νL ν = 9 × 10^6 L_⊙), in the luminosity gap between novae and typical supernovae (SNe). Spectra during the outburst show a red continuum, Balmer emission with a velocity width of ≈400 km s^(−1), Ca II and [Ca II] emission, and absorption features characteristic of an F-type supergiant. The spectra and multiband light curves are similar to the so-called "SN impostors" and intermediate-luminosity red transients (ILRTs). We directly identify the likely progenitor in archival Spitzer Space Telescope imaging with a 4.5 μm luminosity of M_([4.5]) ≈ −12.2 mag and a [3.6]–[4.5] color redder than 0.74 mag, similar to those of the prototype ILRTs SN 2008S and NGC 300 OT2008-1. Intensive monitoring of M51 with Spitzer further reveals evidence for variability of the progenitor candidate at [4.5] in the years before the OT. The progenitor is not detected in pre-outburst Hubble Space Telescope optical and near-IR images. The optical colors during outburst combined with spectroscopic temperature constraints imply a higher reddening of E(B − V) ≈ 0.7 mag and higher intrinsic luminosity of M_r ≈ −14.9 mag (νL_ν = 5.3 × 10^7 L⊙) near peak than seen in previous ILRT candidates. Moreover, the extinction estimate is higher on the rise than on the plateau, suggestive of an extended phase of circumstellar dust destruction. These results, enabled by the early discovery of M51 OT2019-1 and extensive pre-outburst archival coverage, offer new clues about the debated origins of ILRTs and may challenge the hypothesis that they arise from the electron-capture induced collapse of extreme asymptotic giant branch stars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Jencson, Jacob E.0000-0001-5754-4007
Adams, Scott M.0000-0001-5855-5939
Bond, Howard E.0000-0003-1377-7145
Van Dyk, Schuyler D.0000-0001-9038-9950
Kasliwal, Mansi M.0000-0002-5619-4938
Bally, John0000-0001-8135-6612
Blagorodnova, Nadja0000-0003-0901-1606
De, Kishalay0000-0002-8989-0542
Fremling, Christoffer0000-0002-4223-103X
Yao, Yuhan0000-0001-6747-8509
Barbarino, Cristina0000-0002-3821-6144
Sollerman, J.0000-0003-1546-6615
Miller, Adam A.0000-0001-9515-478X
Malkan, Matthew0000-0001-6919-1237
Andreoni, Igor0000-0002-8977-1498
Bellm, Eric C.0000-0001-8018-5348
Frederick, Sara0000-0001-9676-730X
Gal-Yam, A.0000-0002-3653-5598
Gehrz, R. D.0000-0003-1319-4089
Graham, Matthew J.0000-0002-3168-0139
Hankins, Matthew J.0000-0001-9315-8437
Helou, George0000-0003-3367-3415
Ho, Anna Y. Q.0000-0002-9017-3567
Jurić, Mario0000-0003-1996-9252
Kulkarni, S. R.0000-0001-5390-8563
Masci, Frank J.0000-0002-8532-9395
Neill, James D.0000-0002-0466-1119
Riddle, Reed0000-0002-0387-370X
Rusholme, B.0000-0001-7648-4142
Soumagnac, Maayane T.0000-0001-6753-1488
Tachibana, Yutaro0000-0001-6584-6945
Tinyanont, Samaporn0000-0002-1481-4676
Walters, Richard0000-0002-1835-6078
Additional Information:© 2019 The American Astronomical Society. Received 2019 April 12; revised 2019 June 3; accepted 2019 June 5; published 2019 July 26. We thank J. Prieto and E. Ofek for valuable discussions in revising this work. We also thank the anonymous referee for their helpful comments, which improved the manuscript. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under grant No. DGE-1144469. H.E.B. acknowledges support from program numbers GO-14258 and AR-15005, provided by NASA through grants from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This work is part of the research programme VENI, with project number 016.192.277, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO). A.G.-Y. is supported by the EU via ERC grant No. 725161, the ISF, the BSF Transformative program and by a Kimmel award. R.D.G. was supported by NASA and the United States Air Force. Based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. This work was supported by the GROWTH project funded by the National Science Foundation under grant No. 1545949. SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. The work presented here is based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. We thank the Apache Point Observatory Observing Specialists for their assistance during the observations. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. Based on observations obtained at the Gemini Observatory acquired through the Gemini Observatory Archive and processed using the Gemini IRAF package, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Some of these observations are associated with program #15675. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Facilities: PO:1.2 m (ZTF) - , PO:1.5 m (SEDM) - , Hale (DBSP - , WIRC - , TripleSpec) - , NOT (ALFOSC) - , Gemini:Gillett (GMOS) - , Keck:I (LRIS) - , Keck:II (NIRC2) - , ARC (NICFPS - , ARCTIC) - , Spitzer (IRAC) - , HST (ACS - , WFC3) - , WISE. - Software: AstroDrizzle (Hack et al. 2012,, DOLPHOT (Dolphin 2000, 2016), IRAF (Tody 1986, 1993), Gemini IRAF package (, PyRAF (, pyraf-dbsp (Bellm & Sesar 2016,, LPipe (Perley 2019,
Group:Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility, Astronomy Department
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)016.192.277
European Research Council (ERC)725161
Israel Science FoundationUNSPECIFIED
Binational Science Foundation (USA-Israel)UNSPECIFIED
Association of Universities for Research in Astronomy (AURA)UNSPECIFIED
Gemini PartnershipUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:circumstellar matter – galaxies: individual (M51) – stars: evolution – stars: variables: general – stars: winds, outflows – supernovae: individual (M51 OT2019-1)
Issue or Number:2
Record Number:CaltechAUTHORS:20190619-074207862
Persistent URL:
Official Citation:Jacob E. Jencson et al 2019 ApJL 880 L20
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96510
Deposited By: Tony Diaz
Deposited On:19 Jun 2019 17:36
Last Modified:16 Nov 2021 17:21

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